Propeller blades may include a structural spar to increase the structural strength of the blade. The structural spar may include an I-beam stiffener therein to further improve structural integrity thereof. However such stiffeners may be subject to delamination, for example between the I-beam and other spar materials. Delaminations may induce scratches in the blade during manufacture and lead to reduced service life of the blade. The delaminations also require expensive periodic inspections. Furthermore I-beams can be distorted during manufacture particularly when being compressed by a closing resin mould, for example, this can also result in delamination or undesirable radii geometry.